Joseph Smith recorded _
"I told the brethren that the Book of Mormon was the most correct of any book on earth, and the keystone of our religion, and a man would get nearer to God by abiding by its precepts, than by any other book." History of the Church, 4:461
This statement presents a lot of questions. The most obvious being what of the Doctrine and Covenants and Pearl of Great Price? Are these books less correct than the Book of Mormon?
I believe that Joseph Smith wasn't thinking of the D&C and PofGP as finished books at the time of making this statement. After all additions to them were made afterward, by himself. I believe his statement refers to the Book of Mormon relative to the Bible. He is presenting that as the Bible has been doctored, the Book of Mormon is more correct.
Yet still on the title page of the Book of Mormon, Moroni states _
"And now, if there are faults they are the mistakes of men; wherefore, condemn not the things of God" Introduction, Title Page
So Moroni has accepted that mistakes can still occur when man is writing or dictating Scripture. And he has accepted that such mistakes can exist in the work they have put on gold plates. Additionally several times throughout the Book of Mormon the writers refer to the problems they have expressing their real meanings, due to the sloppiness of hieroglyphics.
Moroni states _
"...and if we could have written in Hebrew, behold, you would have had no imperfection in our record." Mormon 9:33
So again we have Moroni stating that imperfections exist in the Book of Mormon. Yet he believes that writing in Hebrew would resolve the problem.
Another point that members tend to raise in a positive light for the Book of Mormon relative to other sets of our Scriptures, is that it is written for our day. However that isn't correct. It would be correct to say that it was compiled on the gold plates for our value today. But it was written for the people at the time. Alma (for example) was not writing to us. He was writing for the value of his people. As surely as Moses wasn't writing in the Old Testament to us just because we have it today either. He was writing to the people of his time mostly.
In regard the Doctrine and Covenants it states at the front _
"The Doctrine and Covenants is a collection of divine revelations and inspired declarations given for the establishment and regulation of the kingdom of God on the earth in the last days." Explanatory Introduction
So the D&C was written for our time much more than the Book of Mormon was.
The completing of the D&C and PofGP as finished books brings them equal status as Keystones to our religion. The D&C contains many unique doctrines that aren't contained in the Book of Mormon. And the PofGP teaches many different things. The whole concept of continued revelation is more evident by the creation of the D&C than the one off revelatory interpretation of the gold plates.
This brings us down to the question of whether the Book of Mormon will get you nearer to God by abiding by its precepts than the Doctrine and Covenants or Pearl of Great Price? This is one place where the Book of Mormon wins. The teachings that Christ presented in the ancient Americas contain the fulness of the gospel of Jesus Christ in its perfect form. There is nowhere else where it is more clearly stated than in 3rd Nephi.